Mat cutter

ABSTRACT

A device for cutting mats for picture frames and the like, comprising an elongate base on which sheet stock can be placed, and an elongate clamp bar coextensive with the base and adapted to engage the stock to hold it in position for cutting. Disposed at opposite ends of the base are two pivotally mounted cams which engage cam followers carried by opposite ends of the clamp bar. Attached to the cams are arms which in turn carry an elongate handle. The bar is vertically movable between an advanced (lower) position with respect to the base wherein it tightly engages sheet stock placed the latter, and a retracted (raised) position wherein it is spaced a distance above the upper surface of the base. Movement of the bar is effected by means of the cams which are located near its opposite ends. A detent portion of each cam operates to retain the handle in a raised position off the surface of the base when the clamp bar is disposed in its retracted (raised) position, such that the base surface is free of obstruction. By such an arrangement, both hands of the operator are free for positioning the stock on the base. A pair of pre-stressed blades, carried on a carriage, slides along the clamp bar and effects the cutting of the mat or stock. The prestressing reduces bending of the blade when it engages the stock, resulting in a straighter, more uniform cut than would otherwise be possible.

United States Patent 1191 Martin MAT CUTTER [22] Filed: May 21, 1974[21] Appl. No.: 471,867

[76] Inventor:

[52] [1.5. CI. 83/455; 83/459; 83/468; 83/614; 269/89; 269/229; 269/236[51] Int. Cl 326d 7/02; B26d 1/06; B26d 3/02 [58] Field of Search83/455, 459, 468, 614, 83/353; 269/89, 91, 229, 232, 233, 236

[56] References Cited UNITED STATES PATENTS 301.418 7/1884 Williams269/233 X 1,560,808 11/1925 Steele 83/452 X 3,213,736 10/1965 Keeton83/455 3,447,409 6/1969 Lewis..." 83/614 X 3,532,018 10/1970 Szabo83/455 Primary Examiner-Willie G. Abercrombie Attorney, Agent, orFirml-l. Gibner Lehmann; K. Gibner Lehmann [57] ABSTRACT A device forcutting mats for picture frames and the Aug. 5, 1975 like, comprising anelongate base on which sheet stock can be placed, and an elongate clampbar coextensive with the base and adapted to engage the stock to hold itin position for cutting. Disposed at opposite ends of the base are twopivotally mounted cams which engage cam followers carried by oppositeends of the clamp bar. Attached to the cams are arms which in turn carryan elongate handle. The bar is vertically movable between an advanced(lower) position with respect to the base wherein it tightly engagessheet stock placed the latter, and a retracted (raised) position whereinit is spaced a distance above the upper surface of the base. Movement ofthe bar is effected by means of the cams which are located near itsopposite ends. A detent portion of each cam operates to retain thehandle in a raised position off the surface of the base when the clampbar is disposed in its retracted (raised) position, such that the basesurface is free of obstruction. By such an arrangement, both hands ofthe operator are free for positioning the stock on the base. A pair ofpre-stressed blades, carried on a carriage, slides along the clamp barand effects the cutting of the mat or stock. The pre-stressing reducesbending of the blade when it engages the stock, resulting in astraighter, more uniform out than would otherwise be possible.

12 Claims, 21 Drawing Figures SHEEI' PATENTEU AUG 5 I 75 I w l ll iu HII PI I I mm wn MET PAIENTEU AUG 51975 3 RES mm Q E SHEET PATENTEI] AUG51975 MAT CUTTER BACKGROUND This invention relates generally topicture-frame matcutter devices, and more particularly to devices ofthis type which employ a base and a retractable clamp bar slidablycarrying a carriage on which there are mounted cutting blades.

A prior device of the kind noted is disclosed in U.S. Pat. No.3,213,736, showing a mat cutter including a base, a clamp bar engageablewith the base, and arms carried by the bar and pivotally mounted at oneside of the base such that the bar can be swung upward away from thecutting surface during the positioning on the base of sheets of materialto be cut. The bar has a slide carriage which holds a cutting blade. AT-square device extends substantially beyond one longitudinal side edgeof the base.

While the above device functioned acceptably well, there were severaldrawbacks to the particular arrangement that had been devised. When thebar was raised off the base and swung to an oppositely disposed, extremeposition, as during placement of a piece to be cut, it extended asubstantial distance beyond the side of the base, often requiring thatthe operator stretch a considerable amount when undertaking such anoperation. In addition, there was a tendency for the bar to interferewith the movement of the operator while he was working. Furthermore, ifit was desired to momentarily raise the bar, one hand was alwaysrequired to hold it in the raised position, leaving only the other handfree for positioning the stock, adjusting the T-square, etc.

Other disadvantages included the fact that in the prior device, theT-square protruded a substantial distance beyond the extremities of thebase, increasing the likelihood that it would be bumped, jarred orotherwise damaged during shipping, storage or even while in use. Wherethe cutting blade engaged the bar for guidance, there frequentlyresulted rapid wear and dulling of the blade, as well as the emergenceof small marks or nicks in the edge of the bar after prolonged use. Inconstructions where the blade was supported at a point remote from thecutting edge, there was a likelihood of detrimental flexing of the bladeduring the cut, such flexing causing crooked edges, uneven cuts, andother undesirable characteristics.

SUMMARY The above drawbacks and disadvantages of prior picture-framemat-cutter devices are obviated by the present invention which has foran object the provision of a novel and improved mat cutter which issimple in construction, reliable in operation and which is considerablyeasier and more convenient to use than devices heretofore known. Arelated object is to provide a mat cutter device which enables theoperator to use both hands in positioning stock to be cut, byeliminating the need to hold a clamp bar in a fixed position. A stillfurther object is to provide a device as above, which is rugged andsturdy in construction and which is not likely to be damaged duringstorage, shipping or use. Yet another object is to provide a devicewhich yields a straightline cut without the use of a cutting bladeguide, thus resulting in greatly improved performance and longer life ofthe blade.

The above objects are accomplished by a cutter device for picture framemats comprising an elongate base having an upper surface on which thesheet material to be cut is placed, and an elongate clamp bar which iscoextensive with the base and which holds in place the sheet material.The clamp bar is movable with respect to the base between an advancedand a retracted position. In accomplishing this, the ends of the clampbar are received in guide members on the base, and carry cam followerswhich respectively engage cams pivotally mounted on the opposite ends ofthe base. Attached to the cams are arms which carry an elongate handle.Movement of the handle in one direction causes the cam followers toadvance the clamp bar toward the base and eventually into engagementthere with. The cam has a detent portion such that when the handle ismoved in the opposite direction, it can be held in a raised positionwith respect to the base, wherein the clamp is retracted. Thus, underthis latter circumstance, the operator has both hands free to positionthe material to be cut.

The bar has a slidable carriage which mounts a pair of cutting blades.The latter are pre-stressed or bent such that a minimum of flexing ofthe cutting edges occurs as the cuts are being made. Especially straightand uniform edges are thus realized by the present engagement.

Other features and advantages will hereinafter appear.

In the drawings, illustrating a preferred embodiment of the invention:

FIG. 1 is a top plan view of the improved mat cutter device of thepresent invention, shown with the clamp bar thereof disposed in theadvanced position with respect to the base.

FIG. 2 is a right end elevation of the cutter device of FIG. 1.

FIG. 3 is a view like FIG. 1, except showing the clamp bar in the raisedor retracted position with respect to the base.

FIG. 4 is a front elevation of the cutter device of FIGS. 1-3, shownwith the clamp bar in the raised or retracted position with respect tothe base.

FIG. 5 is a fragmentary section taken on line S5 of FIG. 1.

FIG. 6 is a fragmentary section takenon line 6-6 of FIG. 1.

FIG. 7 is a fragmentary section taken on line 7-7 of FIG. 6.

FIG. 8 is a fragmentary section taken on line 8-8 of FIG. 6.

FIG. 9 is a top plan view of a support plate constituting one part of arocker assembly for pivotally mounting a first cutting blade on thecarriage.

FIG. 10 is a section taken on line l0l0 of FIG. 9.

FIG. 11 is a bottom plan view of the support plate of FIGS. 9 and 10.

FIG. 12 is a top plan view of a cover plate constituting another part ofthe rocker assembly for pivotally mounting the first cutting blade onthe carriage, the cover plate being adapted to abut the support plate ofFIGS. 9-11.

FIG. 13 is a view taken on line l3 13 of FIG. 12.

FIG. 14 is a top plan view of a support plate constituting one part of asecond rocker assembly for pivotally mounting a second cutting blade onthe carriage.

FIG. 15 is a section taken on line 15-15 of FIG. 14.

FIG. 16 is a bottom plan view of the support plate of FIGS. 14 and 15.

FIG. 17 is a top plan view of a cover plate constituting another part ofthe second rocker assembly for pivotally mounting the second cuttingblade on the carriage, the cover plate being adapted to abut the supportplate of FIGS. 14-16.

FIG. 18 is a view taken on line 1818 of FIG. 17.

FIG. 19 is a diagrammatic representation of the cam as employed to raiseand lower the clamp bar of the mat cutter of the present invention, andshowing a circular rod carried by one end of the bar, the rodconstituting a cam follower.

FIG. 20 is a fragmentary section taken on line 20-20 of FIG. 2.

FIG. 21 is a fragmentary section taken on line 2121 of FIG. 2.

Referring to FIGS. 1-4 there is illustrated a mat cutter devicegenerally designated by the numeral comprising an elongate base 12having a flat upper surface adapted to receive sheets of material to becut, and an elongate clamp bar 14 which is coextensive with the base andmovable with respect thereto between an advanced position wherein itengages the base, and a raised or retracted position wherein it isdisposed off the surface of the base. The advanced and retractedpositions of the clamp bar are illustrated respectively in FIGS. 2 and3. As shown in FIGS. 1 and 6, the bar comprises a flat section 16 whichis pinned to an upper rodlike section 18 of circular cross section. Thebase has a groove 20 in its upper surface and coextensive with the bar14, the groove constituting a recess to receive an edge of one of twocutting blades which are disposed on a carriage to be described below.

Referring to FIGS. 1-4, 20 and 21, and in accordance with the presentinvention there is provided a guide means carried on the base 12 andengageable with the opposite ends of the clamp bar 14 for enablinglimited vertical movement of the latter with respect to the base, theguide means comprising a pair of upstanding guide members 24 havingvertical slots 28 in which there are received slide blocks 32, thelatter having holes 34 engageable with the ends of the rod-like section18 of the clamp bar 14 so as to constitute a guide for the latter as itundergoes vertical movement with respect to the base.

By the present invention there is further provided a pair of springs 36carried by the guide members and engaging the slide blocks, tending tobias the clamp bar to an advanced (lowered) position as illustrated inFIG. 2. In accomplishing this, the slide blocks have vertical holes 38(FIGS. 20, 21) of slightly larger diameter than that of the spring andwhich receive the latter such that it can bear directly against the endsof the rod-like section 18. These ends have flatted portions 40 (FIG.21) which abut the spring, and it can be seen that the latter tends toprevent any turning movement of the rod. Thus the clamp bar 14 ismaintained in a fixed rotary position with the flat section 16substantially parallel to the base 12 at all times.

By the present invention, the opposite ends of the base 12 respectivelycarry cams 42 which are pivotally mounted thereto and can undergomovement between extreme rotary positions as illustrated in FIGS. 2 and3. The cam is shown diagrammatically in FIG. 19. The ends of therod-like section 18 extend to these earns 42 and engage the same, in themanner of a cam follower. Arms 44 extend from each cam at the oppositeends of the base, and an elongate handle 46 coextensive with the basejoins the arms for simultaneous actuation of the two cams. The cams havedetent portions or notches 48, respectively (FIG. 19) which tend tomaintain them in fixed positions when the handle is raised as shown inFIG. 3. This results from the action of the springs 36 and the weight ofthe clamp bar 14 which urge the cam follower or rod 18 into engagementwith the notch. This arrangement has the distinct advantage that thehandle 46 will remain in the raised position of FIG. 3 without having tobe held by the operator, thus leaving both of the operators hands freefor other activity such as positioning the material on the base, etc. Itis noted that for this position, the clamp bar 14 is disposed in itsraised, retracted position (FIG. 3) to facilitate the placement ofmaterial thereunder for subsequent cutting. In addition, each cam has ahook portion 50 which, when the handle is disposed in the loweredposition of FIG. 2, bears against the respective cam follower 18 andtends to hold the clamp bar in tight engagement with the mat or materiallying on the base. Thus, inadvertent shifting of such material islargely eliminated and there is no need to app downward pressure toeither the handle or the clan. bar during such a cutting process.

Referring to FIGS. 1 and 6-8 there is illustrated a carriage or slideblock 54 which has a recess 56 of circular cross-section adapted toreceive the rod-like section 18 of the clamp bar 14 such that thecarriage can undergo sliding movement with respect thereto. The section18 thus constitutes a track for the carriage S4. The block 54 has asubstantially vertical surface 58 and an oblique surface 60 whichrespectively receive rocker assemblies 64, 62. Each rocker assemblycarries a cutting blade 68, 66 respectively, and has handles or knobs72, 70 by which the operator can grasp the respective rocker to effecttilting movement thereof with respect to the carriage slide block 54, soas to bring the respective blade 68, 66 into engagement with thematerial being cut. The rocker assembly 62 comprises two flat plates, asupport plate 74 particularly illustrated in FIGS. 9-11 and a coverplate 76 particularly illustrated in FIG. 12. The support plate 74 hastapped holes 78, 80 which are adapted to align with corresponding holes82, 84 in the cover plate 76, the latter being secured to the plate 74by means of screws. In FIGS. 9 and 10 there is a shallow recess 88 inone surface, the recess being adapted to provide clearance for the blade66 when the plates 74, 76 are clamped together as in FIG. 13. Anadditional countersunk hold 90 receives a screw 92 which extends into atapped hole 94 in the carriage slide block 54, the screw 92 not bearingtightly against the plate 74 so as to enable limited rocking movementthereof about the axis of the screw. The cover plate 76 has a mountinghole 96 for securing the handle or knob 70.

In accordance with the present invention a portion or corner 98 of theplate 74 is relieved, such that the corresponding corner 100 of thecover plate 76 extends a distance beyond. A small ledge or shoulder 102(FIG. 13) is provided on one surface of the plate 76, the shoulderbearing against the blade 66 near its cutting edge when it is sandwichedbetween the plates 74, 76. This imparts a slight curvature to the blade66 as shown in FIG. 13. l have found that such an arrangement whereinthe blade 66 is prestressed in a direction into the cut of the materialprovides a straighter and more uniform cut than would otherwise bepossible in the absence of such prestressing. Less flexing tends tooccur during the cutting since the blade is already partially stressed.I have found this to be a superior arrangement which provides cut edgesof excellent quality. The blade 66 is held in place by means of a thumbscrew 104 which is shown in FIG. 6, and which clamps against one side ofthe blade when the screw is tightened. The rocker assembly is retainedin an upright, nontilted position by means of a spring 106 having oneend secured to the carriage slide block. Replacement of the blade 66 iseffected by loosening of the thumb screw 104, sliding the bladelongitudinally of the plates, and substituting a new blade. The tiltedposition and the upright position of the rocker assembly are determinedby the engagement of a stud I07 carried thereon which is received in anelongate slot 109 (FIG. 7) in the oblique surface of the carriage slideblock.

The parts making up the rocker assembly 64 are particularly illustratedin FIGS. [4-18, and comprise a support plate 108 (FIGS. 14-16) and acover plate 110. The two plates are adapted to abut one anotherbroadside, with the cutting blade 68 sandwiched therebetween, as in theprevious rocker. The assembly 64 is pivotally mounted on the verticalwall surface 58 of the carriage slide block 54 (FIG. 6). As illustratedin FIGS. 14-16, the support plate 108 has tapped holes 111, 112 adaptedto align with corresponding holes 116, I14 respectively on the coverplate 110. The support plate has a countersunk hole 117 which receives ascrew 115 carried by the vertical surface 58 of the carriage slide block54, the rocker assembly being capable of pivotal movement about the axisof this screw. The support plate 108 has a slightly recessed surface 118to receive the blade 68. One corner 119 of the plate is recessed, suchthat the corresponding corner 120 of the cover plate extends beyond it.By the present invention there is provided a raised ledge or shoulder122 (FIG. 18) on the cover plate 110 such that when the blade 68 isclamped between the plates, it is given a pre-stress or bend as in FIG.18. This pre-stressing results in a more uniform, straight cut thanwould be otherwise possible, and I have found it to be a very desirablefeature of the present device. A thumb screw 124 (FIG. 6) clamps againstthe blade 68 to hold the latter in place. As in the previous rockerassembly, the tilted and upright positions are defined by the engagementof a stud 125 carried by the rocker and the ends of an elongate grooveor recess 127 (FIG. 8) in the upright surface 58 of the carriage slideblock.

Referring to FIGS. 1, 2, 4 and 5, there is illustrated a T-square devicefor positioning sheets of material on the base with edges in parallelrelation to the clamp bar 14. The device comprises a slide member 126, abase mounted support track 128 and squaring edge 130. The track 128 isrecessed in the base and has a groove 132 (FIG. 5) to receive the slidemember 126. The latter is provided with calibrating indicia 134, which,together with a pointer 136 on the support track, enables precisesetting of the position of the square. An adjustment screw 138 carriedon the support track can be tightened once the square is in position, toleave the hands of the operator free during the cutting operation. Thepresent construction has the advantage that the square can be set to aposition wherein it has completely within the confines of the oppositelongitudinal edges of the base. This enables the mat cutter to bereadily stored, shipped, and used without likelihood of the squaringapparatus being inadvertently bumped or broken. Prior mat cutter deviceswhich employed protruding type T-squares were prone to misalignment ordamage due to such bumping or jarring. The present constructioneffectively overcomes this disadvantage. Although the T-square is shownin FIGS. 1 and 2 as extending beyond the edge of the base, it will beunderstood that it can be slid to a position wherein the edge overliesthe base with no portions extending beyond the edges thereof.

To facilitate positioning of the material to be cut on the base of thedevice, an additional squaring edge 140 (FIG. 1) is provided, this edgebeing disposed at one end of the base and being perpendicular to theclamp bar 14. The edge 140 is constituted as two separate pieces toprovide clearance for the clamp bar in the advanced position.

In operation, the clamp bar is first raised to the retracted position ofFIG. 3, and the material to be cut placed on the base. It will be notedthat the upright rocker assembly 64 is adapted for making perpendicularedge cuts in the mat, while the oblique rocker assembly 62 is adaptedfor making angular or bevelled edge cuts, the latter being of the typenormally employed to border and overlie the edges of a picture, yieldingan especially pleasing, finished appearance. The carriage is positionedover the area where the cut is to begin, and depending on what type ofedge is de sired, either the straight or the oblique rocker assemblageis tilted, via the respective knob 72, 70, such that the blade piercesthe mat. The carriage is then slid with the rocker tilted, until thedesired cut is achieved. The groove 20 provides a recess for the blade68, such that the latter engages only the mat being cut and not thebase. Following the cut, the clamp bar can be raised for repositioningthe stock for a subsequent cut, etc. Due to the unique arrangement ofthe clamp bar, both of the operator's hands are free for suchrepositioning. Furthermore, by the present construction, there is noneed for the operator to employ one hand to hold the clamp bar downduring the cutting operation. The cam automatically accomplishes thisresult. The device is thus seen to be very easy and convenient to use.

From the above it can be seen that I have provided a novel and improvedmat cutter device which is simple in construction, reliable in operationand which is especially easy to use. Cuts of superior quality have beenachieved with this device, even by persons generally unskilled in thisfield. The device is thus seen to represent a distinct advance andimprovement in mat cutter technology.

Variations and modifications are possible without departing from thespirit of the invention.

I claim:

I. A mat cutter construction, comprising in combination:

a. an elongate base on which sheet stock can be placed for cutting intomats,

b. a flat, elongate clamp bar coextensive with said base,

c. means carried by the base and engageable with stock placed thereon,for positioning the latter with portions thereof disposed under theclamp bar,

d. guide means at each end of the base, engageable with the clamp bar toprovide for advancing and retracting movement with respect to the base,

e. cam followers carried by the ends of the clamp bar for effectingmovement thereof.

f. cams pivotally carried by the base and respectively engaging said camfollowers,

g. a pair of arms respectively attached to said cams for actuating thesame, and

h. an elongate handle coextensive with said base and at its ends securedto said arms to operate the same,

. said handle rigidly connecting the cams and constituting the soleconnecting linkage therebetween, j. said handle further beingsubstantially parallel to and coextensive with said clamp bar and beingdisposed in spaced relation with respect thereto,

k. movement of said handle causing simultaneous pivoting of said camsand movement of said clamp bar.

2. The invention as set forth in claim 1, wherein:

a. said guide means comprises a pair of upstanding guide membersdisposed near opposite ends of and carried by the base,

b. said members each having an elongate guide slot substantiallyperpendicular to the plane of the base, and

c. slide blocks slidably carried in said guide slots respectively, saidblocks having means engageable with the ends of the clamp bar to enablevertical movement thereof as the blocks slide along the slots in theguide members.

3. The invention as set forth in claim 2, and further including:

a. spring means carried by the guide members and biasing the clamp barinto engagement with the base toward the advanced position with respectthereto.

4. The invention as set forth in claim 3, wherein:

a. at least one of said cams has a detent portion adapted to receive therespective cam follower when the clamp bar is disposed in the retractedposition, so as to retain the latter in said position against the actionof said spring means.

5. The invention as set forth in claim 1, and further including:

a. spring means carried on said base and engaging said clamp bar forbiasing the latter toward the advanced position with respect to thebase,

b. said clamp bar having flatted portions at its ends,

c. said spring means engaging said flatted portions and preventingrelative turning movement of the bar with respect to the base.

6. The invention as set forth in claim I, wherein:

a. said clamp bar has a track extending substantially along its entirelength,

b. a carriage slidably movable along said track,

0. a cutting blade disposed on said carriage, and

d. means pivotally mounting the blade for tilting movement on saidcarriage, said blade being advanceable toward said base for engagementwith stock placed thereon in response to pivoting of said mountingmeans.

7. The invention as set forth in claim 1, wherein:

a. said handle is movable between advanced and retracted positions withrespect to the base,

b. the retracted position of said handle corresponding to the retractedposition of said clamp bar such that during the placement of stock to becut on the base, both the clamp bar and handle are clear of the base soas to not cause interference with the stock.

8. The invention as set forth in claim 1, wherein:

a. said cams have hooked portions respectively engaging the camfollowers when the clamp bar is disposed in the advanced position withrespect to the base,

b. said hook portions urging the clamp bar tightly into engagement withthe base thereby firmly hold ing the stock in position during thecutting operation.

9. The invention as set forth in claim 1, and further including:

a. means disposed on the base providing a squaring edge for positioningan edge portion of stock on the base in squared relation with respect tosaid clamp bar.

10. The invention as set forth in claim 9, wherein:

a. said positioning means comprises a T-square having a body portionrecessed in the base and slidable therein, and a straight edge portionadapted to overlie the upper surface of the base,

b. said T-square being slidable to a position lying substantiallycompletely within the confines of the base, to facilitate storing andshipping of the cutter.

11. In a mat cutter construction, the combination of:

a. an elongate, flat clamp bar adapted to press against the uppersurface of sheet-like stock to hold the same for cutting,

b. said clamp bar having a track extending along its length,

c. a carriage movable along said track,

d. blade clamping means on the carriage for securing a cutting blade inspaced relation to the clamp bar, said blade being fixedly and immovablysecured to, and being immovable on, said clamping means,

e. said clamping means pre-stressing and bending the blade to minimizelateral movement thereof as it is cutting through the stock, thereby toeffect a straighter cut.

12. The invention as set forth in claim 11, wherein:

a. said blade has a substantially planar configuration,

b. said clamping means comprises two plates having flat surfacesrespectively engageable with the blade,

c. means securing said plates together with the blade sandwichedtherebetween.

d. one of said plates having an edge portion extending beyond thecorresponding edge portion of the other plate,

c. said one edge portion having a raised ledge on its flat surfaceadapted to engage one side of the sandwiched blade and effect saidpre-stressing and bending thereof.

1. A mat cutter construction, comprising in combination: a. an elongatebase on which sheet stock can be placed for cutting into mats, b. aflat, elongate clamp bar coextensive with said base, c. means carried bythe base and engageable with stock placed thereon, for positioning thelatter with portions thereof disposed under the clamp bar, d. guidemeans at each end of the base, engageable with the clamp bar to providefor advancing and retracting movement with respect to the base, e. camfollowers carried by the ends of the clamp bar for effecting movementthereof, f. cams pivotally carried by the base and respectively engagingsaid cam followers, g. a pair of arms respectively attached to said camsfor actuating the same, and h. an elongate handle coextensive with saidbase and at its ends secured to said arms to operate the same, i. saidhandle rigidly connecting the cams and constituting the sole connectinglinkage therebetween, j. said handle further being substantiallyparallel to and coextensive with said clamp bar and being disposed inspaced relation with respect thereto, k. movement of said handle causingsimultaneous pivoting of said cams and movement of said clamp bar. 2.The invention as set forth in claim 1, wherein: a. said guide meanscomprises a pair of upstanding guide members disposed near opposite endsof and carried by the base, b. said members each having an elongateguide slot substantially perpendicular to the plane of the base, and c.slide blocks slidably carried in said guide slots respectively, saidblocks having means engageable with the ends of the clamp bar to enablevertical movement thereof as the blocks slide along the slots in theguide members.
 3. The invention as set forth in claim 2, and furtherincluding: a. spring means carried by the guide members and biasing theclamp bar into engagement with the base toward the advanced positionwith respect thereto.
 4. The invention as set forth in claim 3, wherein:a. at least one of said cams has a detEnt portion adapted to receive therespective cam follower when the clamp bar is disposed in the retractedposition, so as to retain the latter in said position against the actionof said spring means.
 5. The invention as set forth in claim 1, andfurther including: a. spring means carried on said base and engagingsaid clamp bar for biasing the latter toward the advanced position withrespect to the base, b. said clamp bar having flatted portions at itsends, c. said spring means engaging said flatted portions and preventingrelative turning movement of the bar with respect to the base.
 6. Theinvention as set forth in claim 1, wherein: a. said clamp bar has atrack extending substantially along its entire length, b. a carriageslidably movable along said track, c. a cutting blade disposed on saidcarriage, and d. means pivotally mounting the blade for tilting movementon said carriage, said blade being advanceable toward said base forengagement with stock placed thereon in response to pivoting of saidmounting means.
 7. The invention as set forth in claim 1, wherein: a.said handle is movable between advanced and retracted positions withrespect to the base, b. the retracted position of said handlecorresponding to the retracted position of said clamp bar such thatduring the placement of stock to be cut on the base, both the clamp barand handle are clear of the base so as to not cause interference withthe stock.
 8. The invention as set forth in claim 1, wherein: a. saidcams have hooked portions respectively engaging the cam followers whenthe clamp bar is disposed in the advanced position with respect to thebase, b. said hook portions urging the clamp bar tightly into engagementwith the base thereby firmly holding the stock in position during thecutting operation.
 9. The invention as set forth in claim 1, and furtherincluding: a. means disposed on the base providing a squaring edge forpositioning an edge portion of stock on the base in squared relationwith respect to said clamp bar.
 10. The invention as set forth in claim9, wherein: a. said positioning means comprises a T-square having a bodyportion recessed in the base and slidable therein, and a straight edgeportion adapted to overlie the upper surface of the base, b. saidT-square being slidable to a position lying substantially completelywithin the confines of the base, to facilitate storing and shipping ofthe cutter.
 11. In a mat cutter construction, the combination of: a. anelongate, flat clamp bar adapted to press against the upper surface ofsheet-like stock to hold the same for cutting, b. said clamp bar havinga track extending along its length, c. a carriage movable along saidtrack, d. blade clamping means on the carriage for securing a cuttingblade in spaced relation to the clamp bar, said blade being fixedly andimmovably secured to, and being immovable on, said clamping means, e.said clamping means pre-stressing and bending the blade to minimizelateral movement thereof as it is cutting through the stock, thereby toeffect a straighter cut.
 12. The invention as set forth in claim 11,wherein: a. said blade has a substantially planar configuration, b. saidclamping means comprises two plates having flat surfaces respectivelyengageable with the blade, c. means securing said plates together withthe blade sandwiched therebetween, d. one of said plates having an edgeportion extending beyond the corresponding edge portion of the otherplate, e. said one edge portion having a raised ledge on its flatsurface adapted to engage one side of the sandwiched blade and effectsaid pre-stressing and bending thereof.